Technical Field
The present invention relates to a pressure sensor, especially an instant response pressure sensor which does not have any extra press journey before triggering a signal corresponding to an extremely small pressure applied against it due to the fact that the disclosed structure does without having a continuous gap between a piezoresistor and a neighboring element in the thickness direction.
Description of Related Art
FIG. 1 shows a prior art pressure sensor which has a top substrate 10T. A top electrode 11T is configured on a bottom side of the top substrate 10T; a top piezoresistor 12T is configured on a bottom side of the top electrode 11T. A bottom piezoresistor 12B is configured under the top piezoresistor 12T while keeping a continuous space or gap 16 therebetween; and a bottom electrode 11B is configured on a bottom side of the bottom piezoresistor 12B. A bottom substrate 10B is configured on a bottom side of the bottom electrode 11B.
FIG. 2 shows an operation of the prior art
FIG. 2A shows that the pressure sensor displays a current I0 which is zero ampere (I0=0), and a resistance R0 which is infinity (R0=∞) before the pressure sensor is depressed. At this moment, the bottom surface of the top piezoresistor 12T is shown at a position P0.
FIG. 2B shows that the pressure sensor displays a current I1 which is zero ampere (I1=0) and a resistance R1 which is infinity (R1=∞) when it is depressed initially to a status just offset the continuous gap 16 between the two piezoresistors 12T, 12B. In other words, the pressure sensor is depressed at a position where the top piezoresistor 12T just touches the bottom piezoresistor 12B. At this moment, the bottom surface of the top piezoresistor 12T is shown at a position P1.
FIG. 2C shows that the pressure sensor displays a current I2 which is larger than zero ampere (I2>0) and a measurable resistance R2 displayed when it is depressed further more. In other words, the pressure sensor is depressed further more than the position it was as shown in FIG. 2B. At this moment, the bottom surface of the top piezoresistor 12T is at a position P2.
FIG. 3 shows Resistance v. Press Journey for the prior art
FIG. 3 shows that the Y-axis shows Resistance, and the X-axis shows Press Journey. Either the resistance R0 or R1 of the prior art device is infinity when the bottom surface of the top piezoresistor 12T is at a position of either P0 or P1. The resistance of the prior art device is R2 when the bottom surface of the top piezoresistor 12T is at a position of P2 which is a trigger position.